Return only abstract errors (#30)

We returned concrete errors (such as `jsonization.DeserializationError`)
instead of abstract `error`'s. This is a common footgun in Go, see [this
page in Golang's documentation].

Instead, in this patch, we always return the abstract `error`'s.

Fixes #28.

[this page in Golang's documentation]: https://go.dev/doc/faq#nil_error

README.md

@@ -543,15 +543,14 @@ func main() {
 
 	// Serialize to jsonable
 	var jsonable map[string]interface{}
-	var seriaErr *aasjsonization.SerializationError
-	jsonable, seriaErr = aasjsonization.ToJsonable(environment)
-	if seriaErr != nil {
-		panic(seriaErr.Error())
+	var err error
+	jsonable, err = aasjsonization.ToJsonable(environment)
+	if err != nil {
+		panic(err.Error())
 	}
 
 	// Serialize jsonable to string
 	var bb []byte
-	var err error
 	bb, err = json.MarshalIndent(jsonable, "", "  ")
 	if err != nil {
 		panic(err.Error())
@@ -638,12 +637,11 @@ func main() {
 	}
 
 	var environment aastypes.IEnvironment
-	var deseriaErr *aasjsonization.DeserializationError
-	environment, deseriaErr = aasjsonization.EnvironmentFromJsonable(
+	environment, err = aasjsonization.EnvironmentFromJsonable(
 		jsonable,
 	)
-	if deseriaErr != nil {
-		panic(deseriaErr.Error())
+	if err != nil {
+		panic(err.Error())
 	}
 
 	environment.Descend(

_dev_scripts/test_codegen/generate_jsonization_of_classes_with_descendants_test.py

@@ -89,8 +89,8 @@ def main() -> int:
 {I}jsonable, err := aasjsonization.ToJsonable(instance)
 {I}if err != nil {{
 {II}t.Fatalf(
-{III}"Failed to serialize the minimal {model_type}: %s",
-{III}err.Error(),
+{III}"Failed to serialize the minimal {model_type}: %v",
+{III}err,
 {II})
 {II}return
 {I}}}
@@ -138,12 +138,18 @@ def main() -> int:
 func {test_name}(t *testing.T) {{
 {I}jsonable := any("this is not an object")
 
-{I}_, deseriaErr := aasjsonization.{deserialization_function}(
+{I}_, err := aasjsonization.{deserialization_function}(
 {II}jsonable,
 {I})
 
-{I}if deseriaErr == nil {{
-{II}t.Fatal("Expected a deserialization error, but got none.")
+{I}if err == nil {{
+{II}t.Fatal("Expected an error, but got none.")
+{II}return
+{I}}}
+
+{I}deseriaErr, ok := err.(*aasjsonization.DeserializationError)
+{I}if !ok {{
+{II}t.Fatalf("Expected a de-serialization error, but got: %v", err)
 {II}return
 {I}}}
 

_dev_scripts/test_codegen/generate_jsonization_of_enums_test.py

@@ -106,15 +106,21 @@ def _generate_deserialization_fail_for_enum(enum: intermediate.Enumeration) -> S
 func {test_name}(t *testing.T) {{
 {I}jsonable := any("THIS-CANNOT-POSSIBLY-BE-VALID")
 
-{I}_, deseriaErr := aasjsonization.{deserialization_function}(
+{I}_, err := aasjsonization.{deserialization_function}(
 {II}jsonable,
 {I})
 
-{I}if deseriaErr == nil {{
+{I}if err == nil {{
 {II}t.Fatal("Expected a deserialization error, but got none.")
 {II}return
 {I}}}
 
+{I}deseriaErr, ok := err.(*aasjsonization.DeserializationError)
+{I}if !ok {{
+{II}t.Fatalf("Expected a de-serialization error, but got: %v", err)
+{II}return
+{I}}}
+
 {I}pathString := deseriaErr.PathString() 
 {I}if len(pathString) != 0 {{
 {II}t.Fatalf(

aastesting/common_jsonization.generated.go

@@ -535,11 +535,15 @@ func MustLoadMinimalSubmodel() (result aastypes.ISubmodel) {
 		"minimal.json",
 	)
 
+	fmt.Printf("Must read jsonable\n")
 	jsonable := MustReadJsonable(pth)
 
 	container, err := aasjsonization.EnvironmentFromJsonable(
 		jsonable,
 	)
+	fmt.Printf("container: %v\n", container)
+	fmt.Printf("err: %v\n", err)
+
 	if err != nil {
 		panic(
 			fmt.Sprintf(

getting_started/jsonization_from_test.go

@@ -37,12 +37,11 @@ func Example_jsonizationFrom() {
 	}
 
 	var environment aastypes.IEnvironment
-	var deseriaErr *aasjsonization.DeserializationError
-	environment, deseriaErr = aasjsonization.EnvironmentFromJsonable(
+	environment, err = aasjsonization.EnvironmentFromJsonable(
 		jsonable,
 	)
-	if deseriaErr != nil {
-		panic(deseriaErr.Error())
+	if err != nil {
+		panic(err.Error())
 	}
 
 	environment.Descend(

getting_started/jsonization_to_test.go

@@ -42,15 +42,14 @@ func Example_jsonizationTo() {
 
 	// Serialize to jsonable
 	var jsonable map[string]interface{}
-	var seriaErr *aasjsonization.SerializationError
-	jsonable, seriaErr = aasjsonization.ToJsonable(environment)
-	if seriaErr != nil {
-		panic(seriaErr.Error())
+	var err error
+	jsonable, err = aasjsonization.ToJsonable(environment)
+	if err != nil {
+		panic(err.Error())
 	}
 
 	// Serialize jsonable to string
 	var bb []byte
-	var err error
 	bb, err = json.MarshalIndent(jsonable, "", "  ")
 	if err != nil {
 		panic(err.Error())